Molecular Plant Breeding 2025, Vol.16, No.5, 278-286 http://genbreedpublisher.com/index.php/mpb 282 6.2 Epigenetic and transcriptional responses to environmental cues Tea plants have complex epigenetic and transcriptional regulatory mechanisms when exposed to environmental stress. Studies have found that environmental changes can induce differential expression of flavor-related genes, such as terpene synthases and amino acid synthases, thereby affecting the accumulation of aromatic substances (Yu et al., 2020; Zhao et al., 2022; Wu et al., 2023). Post-harvest stress can regulate the expression of genes in the aromatic synthesis pathway through transcription factors (such as CsMYC2c), resulting in differences in aroma components among different varieties (Wu et al., 2023). Treatment with exogenous elements (such as selenium) can also significantly change the expression profile of flavor metabolism genes and improve the quality of tea (Zhang et al., 2025). These molecular responses provide potential targets for molecular breeding and are helpful in screening out superior genotypes with strong environmental adaptability and stable flavor. 6.3 Breeding for stable flavor traits across environments Pan-genome and population genome studies have shown that flavor traits are regulated by multiple genes and have abundant allelic variations and selection signals (Zhang et al., 2021). Through genome-wide association analysis (GWAS) and molecular marker-assisted selection, the major flavor genes and their environmental interaction effects can be precisely located (Rohilla et al., 2022; Chen et al., 2023). Combining epigenetic and transcriptomic data, along with multi-environmental phenotypic assessment, is helpful for screening flavor genotypes that perform well under various terroir conditions and achieving genetic stability of flavor traits (Yu et al., 2020; Zhao et al., 2022). Novel mutagenesis breeding (such as aerial mutagenesis) also provides new approaches for enhancing flavor diversity and environmental adaptability (Ye et al., 2024a). 7 Case Study: Molecular Breeding for Aroma Improvement in Tea 7.1 Selection of high-aroma tea cultivars for genomic analysis The screening of high-aroma tea tree varieties usually relies on rich germplasm resources and phenotypic assessment. Researchers used genome-wide association study (GWAS) and pan-genome construction to sequence the genomes of 22 representative superior varieties, revealing the genetic diversity and functional variations that affect aroma and flavor. These achievements provide important genetic resources for molecular breeding (Zhang et al., 2021; Chen et al., 2023). Metabolomics analysis systematically identified the aroma and flavor metabolites of 136 tea plant samples, clarifying the accumulation patterns of characteristic metabolites among different strains (Yu et al., 2020). 7.2 Identification of key alleles and markers for flavor biosynthesis Researchers have identified key genes and their allelic variations related to aroma and flavor by using genomic and transcriptomic data. The high expression of the linalool synthase gene is closely related to the accumulation of (R)-linalool in high-aroma varieties and is an important molecular indicator of the aroma quality of dark tea (Figure 2) (Li et al., 2022b; Liu et al., 2025). Key enzymes in the aromatic amino acid metabolic pathway (such as AAATs) and their allele variations have also been confirmed to affect the formation of aromatic compounds (Wang et al., 2019). Molecular markers (such as SNP, SSR) have been developed to assist in the selection of high-aroma and high-flavor varieties and accelerate the breeding process. 7.3 Field validation and sensory evaluation of improved lines The improved lines obtained through molecular breeding need to be tested at multiple points in the field and comprehensively verified by combining metabolite analysis and sensory evaluation. Field experiments have shown that new breeding methods such as aerial mutagenesis can significantly increase the content of volatile aroma substances in tea and enhance sensory characteristics such as fruity aroma and floral aroma (Ye et al., 2024a; Ye et al., 2024b). Sensory evaluation combined with gas chromatography-olfactory analysis (GC-O) and flavor dilution analysis (FD) can quantitatively identify key aroma active substances and be correlated with molecular labeling results to ensure the stable performance of improved strains in actual production (Yang et al., 2021; Li et al., 2022a).
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